Welcome to the sharp end of the season – the cruel bit. Imagine being Saracens, on a high after beating Clermont Auvergne on one of the great European days, not making the grand final; or being part of the first Leicester side in a decade not to get to Twickenham on finals day; or a Northampton side that trips up again when the silverware is in sight.

And that is before Wasps, granted a reprieve by the outbreak of peace in the committee rooms, take on Stade, another big beast fallen on less successful times, for the 20th and final place in the new Europe.

It all starts on Friday night with the east Midlands derby at Northampton but I'd like first to address the battle between north and south London and the lingering seismic shocks which followed that Saracens dusting of mighty Clermont. Not even Clermont get over 46-6 defeats in a hurry. They left London reeling, smashed in all areas and within a week coughed up a home streak which had lasted 77 games.

The question now is whether Saracens themselves can continue playing at such lofty levels or whether Harlequins, seemingly out of it a couple of months ago when Saracens sorted them 39-17, have rediscovered the game to make the grand final. If they do it will mean the tightest, most suffocating defence in the Premiership has been undone by the loosest of attacks.

Harlequins have the game and have to use it; they have to attack, they have to unload, because it's a style that can change the dynamics of any defence. But it's difficult and it's risky.

My Worcester played Saracens a couple of weeks ago and, when you analyse them, there are things you can work on but they tend to be taken away from you by the pressure. Saracens' line speed, the way they are in your face, robs sides of time. An offload game can offset that line speed because it doesn't allow time for the defence to reset but it's risky and hard to deliver the levels of skill required when the pressure is on.

That said, Harlequins cannot sit back. The more structured you are against Saracens, the more trouble you're in because they are the best at it and, as they proved against Clermont, Saracens can tackle even the best into submission.

So Harlequins have to be true to themselves. They have to attack; they have to unload. And they have to mix up their game, with not too much of just one thing, because Saracens thrive on predictability. Harlequins have the people – Danny Care to add the tempo, Nick Evans' game management and knowing when to kick, because you have to kick, and Nick Easter to make up that 8, 9, 10 axis – but I can't overstate how difficult it will be in the face of the most physical defence in Europe.

First, though, comes that east Midlands affair, Leicester heading to Franklin's Gardens, a venue at which Tigers are clearly comfortable and against a team their director of rugby, Richard Cockerill, said he would have chosen to play rather than Saracens – a wind-up obviously. But I doubt if it will be getting into the minds of guys like Tom Wood, who know they threw away the title last year. That is what will matter on Fridaynight. Admittedly they are without Dylan Hartley, the culprit that day at Twickenham, but I don't believe they need their captain until the grand final.

This time last year Northampton went to the Allianz and beat Saracens fair and square. OK, Mark McCall's side have moved on since then but Northampton are probably the only Premiership side who can match Saracens for physicality in a grand final that would cap the season.

One cannot ignore Leicester's history in these east Midland derbies but this Tigers team does not have the consistency of form they normally find after Christmas. At this point they would normally have the momentum of a 10-game winning run behind them.

They have some young guys in key positions and, with Toby Flood off to Toulouse, there is an element of transition whereas the whole cycle of the Northampton squad is one that needs and demands success. They have got over the wobbles that came around the time of the Six Nations, when so many of their guys were away.

Ben Foden, left, is back and sharp, Stephen Myler has the kind of kicking stats that could easily see him at fly-half for England in Auckland at the start of next month and Alex Corbisiero could yet have a say in the run-in to the end of the season, although the Waller brothers, Alex and Ethan, have done a more than useful job in the absence of the Lions loosehead.

Only a fool would ever write off Leicester but Saracens – very much the team to beat at the moment – and Northampton – the side which whacked them in the play-offs last season – is the grand final I'd want to watch.